The present invention relates to a process for packaging a product comprising the operations of thermoforming, filling and sealing of recipients of thermoplastics material.
According to a known process for packaging, known in particular by French Pat. No. 1,512,671, a thermoplastics web is unwound from a roller and is advanced step by step, being held on its two edges parallel to its direction of advance, said web is heated, in successive zones, up to its softening temperature and, during each of the successive steps of said web, at least one transverse row of recipients is thermoformed in a forming station in at least one row of forming chambers of a moulding unit in two parts, of which one, the front part, is mobile with respect to the other, so-called rear part. According to this known process, the recipients of at least one row of recipients are simultaneously filled with a product, particularly a liquid or pasty product, the openings of the filled recipients are covered with a covering web which is deposited on the thermoplastics web provided with the thermoformed recipients, said covering web is sealed on the edges of said recipients which are still attached to the thermoplastics web, in a sealing station comprising a lower sealing support of which one part is fixed and another part is mobile. Finally, in a cut-out station, the filled and sealed recipients are detached, in groups or individually, from the thermoplastics web and the covering web which are sealed to each other, and the sealed and cut out recipients are then evacuated, the edges of the recipients and the corresponding zones of the thermoplastics web being supported between the different work stations by supporting and guiding rails extending in the direction of advance of the thermoplastics web and said recipients.
The present invention also relates to an installation for packaging, of the type known by French Pat. No. 1 512 671. This packaging installation comprises a station for unwinding a thermoplastics web, also referred to as web forming the recipients, a station for heating the thermoplastics web, a thermoforming station for simultaneously making in said thermoplastics web at least one transverse row of recipients of which the openings are directed upwardly and comprising a moulding unit which presents a transverse row of forming chambers and is provided with a fixed rear part installed immediately beneath the path of the thermoplastics web and with a mobile part adapted to move away from the path of advance of the recipients. This packaging installation further comprises a station for filling the recipients with a product, particularly a liquid or pasty product, a station for unwinding a covering web, a station for sealing the covering web on the web forming the recipients on the edges of said recipients, this station presenting an upper sealing head and a lower sealing support comprising at least one mobile part so as to be able to move away from the path of advance of the recipients. The packaging installation also comprises a cut-out station comprising an upper cut-out tool provided with mobile upper blades and a lower cut-out tool provided with lower blades, and longitudinal supporting and guiding rails extending in the direction of advance of the thermoplastics web and said recipients as well as means for advancing the thermoplastics web, the recipients and the covering web step by step and means for controlling the different members for heating the thermoplastics web and forming, filling, sealing and cutting out said recipients.
According to the known prior art, the mobile parts of the moulding unit constituted by transverse partitions are withdrawn from the path of the thermoformed recipients in a horizontal transverse direction so that these transverse partitions emerge laterally from the packaging installation and in particular from the horizontal projection of the thermoplastics web forming recipients. Consequently, it is impossible to provide clips or gripping elements adapted to grip on the longitudinal edges of the thermoplastics web and fast with longitudinal endless chains for conveying said thermoplastics web with its recipients through the different work stations of the installation. According to the known state of the art, pairs of conveyor rollers pulling on the thermoplastics web and the covering web sealed thereon have therefore been provided downstream of the cut-out station. It will be readily understood that, to ensure transport of the thermoplastics web with the filled and sealed recipients through the whole installation, considerable efforts must be exerted on said thermoplastics web which very frequently deforms in uncontrollable fashion under the influence of these efforts and under the effect of the contraction of the thermoplastics web. To ensure traction on the webs in this way, there must always be at least one grid of web after the recipients have been cut out, so that it is virtually impossible to effect for the recipients a cut-out without at least longitudinal scrap.
Another drawback of the state of the art resides in the fact that both the lateral parts and the front and rear parts of the recipients must be flat and they join along sharp angles. In addition, the rear part or the front part of these recipients cannot be provided with vertical grooves.
The same drawbacks are due to the particular design of the lower sealing support of which the mobile parts can move only horizontally and transversely to the direction of advance of the recipients.
In the known cut-out station, the lower cutting tool is constituted by a plurality of dies which cooperate with corresponding punches of the upper cutting tool. Taking into account the particular structure of the lower cutting tool, the recipients cannot be detached in groups but only individually and, in addition, the recipients cut out individually must descend through the corresponding die over the whole height thereof before being able to be taken by a conveyor belt. As soon as the recipients have been cut out, they are therefore no longer guided and can no longer be manipulated with precision. Furthermore, it so happens that the individual recipients frequently jam in the vertically mobile dies of the lower cutting tool and provoke stoppages of the installation.
It has also been ascertained that the considerable stroke of the lower cutting tool leads to repeated acceleration and deceleration of the very considerable masses, with the result that the working speed of the whole of the installation is relatively low and large supporting structures must be provided, particularly at the location of the die of the lower cutting tool to absorb the different outstanding efforts without deformation.
A moulding unit is also known (cf. French Pat. Nos. 2 256 818 and 2 439 712) presenting two parts of which the rear part is fixedly installed at the level corresponding to the position of thermoforming of the recipients, and of which the front part may be lowered from the thermoforming position, to clear the passage for the horizontal advance of the recipients which have just been thermoformed. According to this state of the art, the lowering of the mobile front part of the moulding unit serves, in the first place, for the introduction of a decorative element in the different forming chambers and its purpose for the whole installation is neither the reduction in the mobile pieces nor the simplification of the packaging process. In fact, the state of the art illustrated by the two French Patents last mentioned gives no precise indication as to the seal and cut-out of the recipients which are effected in conventional manner and therefore present the well-known drawbacks.
When the thermoformed recipients are of large dimensions, containing for example a volume of one liter, the lateral walls are deformed, forming bulges under the effect of the weight of the contents of the recipients. Taking into account the fairly low rigidity of the lateral walls of the recipients, it should be possible to make a low vacuum in the recipients in order to avoid their bulging outwardly which, with the known cut-out system incorporating punch and die, often leads to the recipients which are insufficiently engaged in the corresponding die, being crushed.